Emulsions of aminofunctional silicones and high molecular weight silicones are widely used in hair care compositions to provide various aesthetic benefits. Various types of emulsions have been commercially developed to provide water based products of such aminofunctional silicone polymers for use as hair conditioning agents. One method to prepare aminofunctional silicone emulsions involves emulsion polymerization techniques, where siloxane monomers are first emulsified, and then subsequently polymerized to a high molecular weight. Alternatively, mechanical emulsions may be prepared from pre-formed aminofunctional silicones.
Reducing the presence of solvents, un-reacted siloxanes, catalyst residues, cyclic polymerization byproducts, and other impurities in silicone emulsions is an ongoing challenge in the art. The need to reduce such impurities may arise, among other reasons, when such impurities are incompatible with downstream applications (for example, medical, cosmetic, and personal care applications), where the presence of such impurities would reduce the stability of an emulsion, or where regulatory requirements require removal or reduction of their presence. In particular, there is an interest to reduce the presence of cyclosiloxanes, such as octamethylcyclotetrasiloxanes and decamethylcyclopentasiloxanes, in silicone emulsions.
The present inventors have discovered a process for producing mechanical emulsions of aminofunctional siloxanes having reduced content of cyclosiloxanes. Thus, the amount of octamethylcyclotetrasiloxanes and decamethylcyclopentasiloxanes in the emulsions produced by the present inventive process is reduced when compared to emulsions prepared by conventional methods. The resulting emulsions are particularly useful in hair care products.